The invention relates to toothed gear systems.
In one well-known form of system, double helical gearing is used in which gear wheels each have two oppositely-handed arrays of external helical teeth which mesh with internal oppositely-handed helical running teeth of two concentric ring gears. The ring gears have external helical coupling teeth by which they are connected to a common coupling member having internal oppositely-handed helical coupling teeth. The common coupling member has external spur coupling teeth by which it is connected to an outer coupling member which has internal spur coupling teeth.
Misalignment between the axis of rotation of the outer coupling member and the common axis of rotation of the ring gears and the inner coupling member is accommodated by relative longitudinal sliding between the spur coupling teeth.